. >>> halfway around the world in cairo today, an explosion of violence aimed at the united states. muslim protesters stormed the u.s. embassy. they're angry over a film they consider insulting to the prophet mohammed. our chief foreign correspondent richard engel is in the region with us tonight from istanbul. what was this about? and was the embassy ever in any real danger? >> reporter: it was never in any real danger, but this could escalate, and the situation remains tense. it all began this afternoon, when several hundred demonstrators gathered in front of the u.s. embassy. then a few dozen of the demonstrators managed to scale the perimeter walls, get inside the embassy, pull down the u.s. flag, replace it with a black islamic flag. then egyptian security forces moved in to secure the perimeter. under the former president, hosni mubarak, this would have been very difficult. protesters wouldn't have been allowed anywhere near the u.s. embassy. today they were able to scribble graffiti on the embassy wall. this was all triggered by a movie, a fringe, radical movie made in the un